The present invention relates generally to equipment employed in the performance of perfusion catheterization procedures, and more particularly, to a pumping apparatus which interconnects an aspiration catheter with a percutaneous transluminal coronary angioplasty (PTCA) catheter or the like to provide a constant, preselected flow of body fluids through the catheter.
The use of inflatable balloon catheters in the treatment of coronary conditions is widespread. Balloon catheters are commonly used to expand blockages in arteries. These blockages are a narrowing of an artery or other body vessel, and are referred to as a stenoses. In PTCA procedures, a guide catheter is introduced into the artery of the patient and guided through the artery until the distal tip of the catheter is at the desired location of the coronary artery near the stenosis. A dilation catheter having an inflatable balloon affixed to its distal end is introduced along the guide catheter and advanced into the patient until the balloon end is located at the stenosis. The balloon is subsequently inflated to expand it against the artery walls to expand, or dilate, the artery and compress the stenosis. This expansion can remove all of or a significant portion of the blockage when the balloon is inflated against the arterial walls for a preselected time or repeatedly inflated and deflated in a cycle to match that of the heartbeat of the patient.
Once the artery has been expanded, the balloon is deflated and it and the guide catheter is removed so the blood again may flow on its own through the artery. Restenosis is a condition where the arterial wall has been initially expanded by the balloon and the arterial blockage is open but the arterial wall contracts and adopts all of or part of its original, restricted state sometime after the balloon is deflated and removed. The rate of restenosis is believed to be lowered if longer inflation times are used during balloon catheterization procedures.
The use of longer balloon inflation times may promote the occurrence of ischemia of the cardiac muscles. Ischemia is a local deficiency of oxygen in an area of the body caused by an obstruction in the blood vessels supplying blood to that area. To prevent ischemia, perfusion catheters are used in association with coronary angioplasty catheters. Perfusion catheters are catheters which permit the continuous flow of blood through the blockage during the inflation of the balloon in the artery.
The perfusion of blood through a balloon at the distal end of a catheter may be accomplished by a balloon having one or multiple passages or lumens which define flow channels extending through the balloon from one end to the other. These passages permit flow of blood past the balloon and through the blockage. A reliable pump must be used to pump blood continuously past the balloon through the balloon passages. In order to avoid ischemia, a specific flow rate past the balloon, such as 60cc per minute is desirable. Generally, perfusion catheters have lumens which are very small and have minute diameters on the order of approximately three mils (0.003 inch). Any external pump used in such perfusion procedures to pump blood through these size catheters must provide a continuous flowrate of blood at high pressures which may approach 300 psi. These high pumping pressures are needed in order to pump blood through small lumens of these catheters, rather than rely upon the patient's heart to pump blood through the lumens past the balloon inflation area. The external pump draws blood from the patient by way of an aspiration catheter and circulates it back through the perfusion catheter and past the distal end of the balloon.
External blood pumps are well-known and have been commonly used for regulating blood through coronary arteries during open-heart surgeries. These pumps generally provide a low pressure output and are not capable of supplying the necessary high pressure to pump blood at the predesired flowrate through the small lumens used in perfusion catheters. A positive displacement pump which uses a conventionally powered piston may create a pressure pulse during its pumping stroke which may result in a pressure transient occurring during pumping. If a single-stroke piston pump is used, it may only at best provide intermittent blood flow because after every pumping stroke, a reversal or suction stroke, must be performed to refill the pump piston. A need therefore exists for reliable perfusion pump which can pump continuously and develop the large pumping pressures needed for perfusion through small diameter catheters.
External perfusion pumps are well known, such as the one described in U.S. Pat. No. 5,066,282 issued Nov. 19, 1991. This patent is directed to a perfusion pump with a pulsation-damping mechanism that serves to smooth out pressure pulses of the pump during pumping. This pump contains only one pumping chamber and relies upon a reservoir to be continuously filled with blood or similar body fluid. No provision is made in this patent for the components of the pump to be entirely disposable, and, due to the pressure damping means incorporated in the pump, it may be expensive to manufacture and difficult to clean.
Other external pumps are known which use syringes as their primary components, such as that described in U.S. Pat. No. 3,447,479, issued Jun. 2, 1967. This patent describes various arrangements of syringe pumps which perform alternating suction and pumping strokes. In the multiple syringe pump arrangement shown in this patent, four syringe pumps are powered by a motor-driven eccentric cam. However, return springs must be used on the plungers of these pumps in order to ensure the prompt return of the pump plungers to their original positions within the syringes. This mechanism is complicated and a possibility exists that the springs and cam may not always reliably power the pumps through a complete suction and pumping cycle because of wear.
The present invention is therefore directed to an external pumping apparatus for use in catheterization procedures, and particularly in perfusion catheterization which continuously and reliably both withdraws blood from a patient and reintroduces the blood back into the patient.
In accordance with one aspect of the present invention, a housing member is provided which supportingly engages two positive displacement pumps, each of the pumps having a plunger slidable within a pump chamber, the plunger of one pump and the chamber of the other pump being fixedly mounted to the housing so as to prevent movement relative to the housing. The one pump chamber and the other pump plunger engage an actuating member slidable within the housing. When the actuating member moves in response to movement of a power cylinder, it imparts a pumping action in the one pump and a suction action in the other pump. Movement of the actuating member in the opposite direction induces a reverse movement in the pump components, so that the one pump will perform a suction stroke while the other pump performs a pumping stroke, whereby the pumping apparatus provides a continuous flow of blood during its operation.
In another aspect of the present invention, two syringe pumps are disposed within a housing, each of the syringes having a plunger slidable within a barrel portion and the housing having two channels in which the syringes are situated. One housing channel engages the plunger of one pump and restrains it from movement relative to its barrel portion, while the other housing channel engages the barrel portion of the other pump and restrains it from movement relative to its plunger. The actuating member reciprocates in the housing parallel to the longitudinal axes of the syringe pumps. The actuating member engages a double acting piston powered by a hydraulic fluid or gas. At any given time during operation of the apparatus, the actuating member engages a plunger member of one pump and a barrel portion of the other pump so that in response to any movement of the piston, the actuating member drives one of the two pumps in a pumping mode and the other pump in a suction mode.
Accordingly, it is an object of the present invention to provide an external perfusion pumping apparatus for use in PTCA and other related catheterization procedures which can readily supply a continuous supply of blood or other body fluids at high pumping pressures required for the perfusion of these fluids through catheter minute diameters.
Another object of the present invention is to provide a pumping apparatus having multiple pump elements supported in a housing, the pumping apparatus including a fluid powered cylinder operatively engaging the pump elements to simultaneously drive one pumping element in a pumping stroke and another pump element in an aspirating, or suction stroke, whereby the pumping apparatus provides a continuous supply of body fluids to a perfusion catheter or other catheter.
Still another object of the present invention is to provide a pumping apparatus for use in perfusion catheterization wherein the pumping apparatus includes two syringe pumps, each having a plunger component slidable within a barrel component, the plunger and barrel components cooperating to define a pumping chamber of variable volume in each syringe pump, each of the syringe pumps being supported within a housing, the two pumps being interconnected by a rod operatively associated with a fluid cylinder wherein movement Of the fluid cylinder imparts a like movement to the actuating member, the fluid cylinder operating in a reciprocating manner such that at any instant during operation of the pumping apparatus, one of the two syringe pumps is constantly withdrawing, or aspirating, blood from a blood source, while the other syringe pump is constantly pumping blood from the blood source into the patient to achieve a continuous flow of blood through the apparatus and into the patient at a preselected flowrate to prevent ischemia or other injury to the heart of the patient from prolonged lack of blood.
Still yet another object of the present invention is to provide an improved pumping apparatus for use in perfusion and other catheterization procedures wherein two syringe pumps are powered by a fluid cylinder such that one syringe pump is maintained in a pumping mode while the other syringe pump is maintained in a suction mode and wherein the fluid cylinder ensures that each of the two syringe pumps returns to its initial operating position after movement by the fluid cylinder without the necessity for return springs or the like.
These and other objects features an advantages of the present invention will be clearly understood through consideration of the following detailed description.